What happened
On the evening of August 24, 2007, a private paramotor, identified as 71-IK, departed from a private ultralight airfield in Anost, France. At approximately 20:15, the aircraft was observed by witnesses flying over the locality of "Les Chauveaux" in Arleuf. During the flight, the pilot performed a right-hand turn at low airspeed.
Witnesses observed that as the aircraft exited the turn, the right side of the wing deflated across approximately one-quarter of its span. This caused the aircraft to bank sharply to the right. During this maneuver, the engine RPM was heard to increase. While the right side of the wing briefly reinflated, the left side subsequently collapsed, leading to a total collapse of the wing. The pilot fell from an estimated altitude of between 50 and 100 meters, resulting in one fatality and the destruction of the aircraft.
The investigation
The investigation focused on the condition of the ITV Proxima 2 wing and the mechanical state of the aircraft. Examination of the wreckage revealed that all lines remained attached to the wing. However, portions of the lines and the right-side brake control were found wrapped around the propeller shaft, with one of the two propeller blades broken. Evidence suggested this entanglement occurred following the impact with the ground.
Technical inspections of the wing determined it was in good condition prior to the accident. However, investigators found that the lengths of the C and D lines (connected to the rear of the wing) were 10 to 20 mm shorter than the manufacturer's specifications. This discrepancy altered the wing profile, creating a tendency to pitch up more significantly than a standard wing of the same type. Additionally, the brake control lines were shorter than recommended, a setting that can cause pilot discomfort and lead to unintentional braking.
Findings
- The wing's profile was modified due to incorrect line lengths, increasing the tendency to pitch up.
- The brake control settings were shorter than specified, which could induce involuntary braking.
- A wing in a braked state is more susceptible to turbulence, particularly during low-speed flight.
- The asymmetric stall may have been triggered by turbulence during low-speed flight.
- The collapse of the left side of the wing and the subsequent total collapse were likely caused by excessive use of the left brake and a premature increase in engine power, which can exacerbate a stall when the wing is outside its normal flight envelope.